This study will evaluate the effects of chronic use of a common herbal remedy, St. John's Wort (Hypericum perforatum) on metabolism of contraceptive steroids and ovarian suppression during oral contraceptive use. St. John's Wort is one of the more popular herbal remedies. It has been implicated as an inducer of the cytochrome P450 enzyme (CYP) system, and as such may cause increased metabolism of certain drugs, including oral contraceptives. Women using oral contraceptives have been warned against using St. John's Wort, although there are to date no data demonstrating risk of contraceptive failure if they do. This will be an open-label, non-randomized, unblinded, sequential treatment clinical trial of reproductive-aged women. Eligible women will take low dose oral contraceptives containing ethinyl estradiol and norethindrone for two months, followed by two months taking the same oral contraceptive and St. John's Wort. Several markers of hormonal and ovarian activity will be evaluated. Parameters to be compared between these two exposure periods are: 1. the pharmacokinetics of contraceptive steroids 2. follicular development in the ovary 3. evidence of ovulation, 4. evidence of the potential for ovulation, 5. the quality of cervical mucus, 6. endometrial proliferation, and 7. irregular vaginal bleeding. This preliminary study will identify possible undesired interactions between a common botanical remedy and oral contraceptives. A concurrent aim is the development and refinement of a methodology for evaluating the risk of ovulation and unintended pregnancy from use of other herbs or medications during oral contraceptive use.